Folded dipole



Oct. 26, 1948. 3 w SCHIVLEY ET AL 2,452,073

FOLDED DIPOLE Filed Nov. 17, 1944 2 Sheets-Sheet 1 FOLDED DIPOLE f/GJ Patented Get. 26, 1948 "UNITED sTA-T.

- ro'nnnn DIPOLE George William Schivley, Buchtel, and Paul W; Springer, Dayton, Ohio Application November 11, 1944, seri 1'No; 563,980

1 Claim." ((21. 250-33155) (Granted under the act ofMarch s, 1883, as

The invention described herein may be manufactured and used by or for the Government for governmental purposes, Without the payment to us of any royalty thereon.

The present invention relates to directional antennae.

An object of the invention is to provide a radio antenna for use on the tail of, an aircraft in circuit with a warning device, to Warn of the presence of another craft in flight within a predetermined range. k

A further object is to provide such an antenna which may be applied to various ypes and sizes of aircraft with a minimum of adjustment. I

A further object is to provide such an antenna which is of light weight, highly directional, of controllable wave pattern and range, simpleto manufacture and install and highly efficient in use.

These and other objects will appear throughout the specification and will be pointed out in the claim.

The use of reflected radio wave'pulse transmitting and receiving instruments to signal the presence of distant objects is particularly indicated for use in warning a pilot in flight, particularly a fighter plane pilot, of the presence of an enemy plane just outside firing range directly behind the tail of his plane.

The difficulties of adapting such radio equipment, however, have centered about the control of the emitted and received radio'waves so that only reflected waves from planes within thevulnerable area behind the tail and within firing range be indicated. If such warning equipment were actuated by neighboring flight formations, ground signal, or planes beyond firing range, it would inevitably endanger and confuse the pilot.

The use of a unidirectional antenna would aid in the direction of the transmitted waves to the rear of the plane. Available antennae, particularly the Yagi type, when applied to the tail fin of a plane, have the disadvantage of requiring individual tuning for every plane since the thickness of the finson different aircraft on'which the antenna is to be mounted, is subject to considerable variation. The necessity for weight reduction of this auxiliary equipment also limits the usefulness of such antenna because of its low efliciency when bilaterally shrouded.

The present invention utilizes a quarterwave two-section unidirectional dipole antenna of the folded type, one section of which is attached to each side of the airplane vertical fin. These two antenna sections are electrically joined together amended April 30, 1928; 370 O. G. 757) by alooped phasing and balancing cable section so that regardless of the spacing between the two sections, any variation in width of fins is automatically taken up by the slack in the loop without in anyway affecting the balancing ortuning of the antenna-transmitter-receiver circuit. By such a laterally adjustable construction, the entire problem of antenna installation to various types and sizes of aircraft becomes so simple that installation may be easily accomplished by inexperienced persons unfamiliar with radio circuit balancing or slotted line technique. Once the size of antenna is established by the manufacturer, in balance with the transmitter and receiver, variation in width of tail fin will not affect the range, direction or pattern of the radiated waves, as is the case with rigid Yagi type antennae, in which covering or uncovering of theprojecting antenna by the fin surface would change the length and consequently the characteristics of the antenna.

Referring to the drawings wherein like numerals denote like parts,

Fig. 1 is a top plan view of the antenna in location with respect to its parasitic reflector, and director;

Fig. 2 is a side elevation on a reduced scale of the antenna shown in Fig. 1, illustrating the normalrelationship of antennaand aircraft-tail fin;

Fig. 3 is an enlarged schematic diagram of the antenna shown in Fig. 2, illustrating the circuit connections;

Fig. 4 is a cross-sectional illustration of the horizontal field or wave pattern obtainable with the antenna herein described; and

Fig. 5 is a vertical cross-section of the wave pattern horizontally sectioned in Fig. 4.

By way of illustration, the preferred embodiment of the invention, as applied to an aircraft tail fin or wing comprises a folded dipole twosection antenna, generally referred to as Ill and composed of two U-shaped rods l [and I2 threaded at their ends for bolting to a pair of assembly plates l3 and I4. Bolted to these plates 13 and I4 in'thepla'ne of the legs of the U-shaped antenna ll andl2 and spaced therefrom a pair of parasitic reflector rods l5 and I6 project outwardly parallel with the U-shaped antenna leg sections H and i2 and for a greater distance. Parallel with and also in the plane of said antenna sections II and l2, 2. pair of director rods l1 and I8 extend from said assembly plates for a distance less than that of either the parasitic reflectors or the antenna sections. Looped between and electrically connecting one of the adjacent ends l9 and 20 of each of the antenna sections the antenna. This length of cable has the efiect: I of dividing the current from conductor 26 equally and I2 and of making the between antennae H currents in these two antennae equal and in con! stant, or like, phase in the sense arrows in Figure 3. Another length o f this coaxial conductor ZSconnects the antenna'andassembly- 4 tween the opposite faces of the tail fin (and consequently of the antenna sections) which is spanned by the coaxial cable loop 2|.

With associated radar equipment the invention has been found highly useful in warning of .the presenceof enemy aircraft behind the tail of @the plane on which the apparatus has been installed. It is obvious that by a suitable wing 1 mounting forward gun range radar may be had.

i dicat d-b th Any radar type transmitting and receiving apparatus within frequency limits may be used with the antenna, so that not only the presence, but

also the range of other aircraft may be indicated.

,;'n conjunction with suitable associated radar plates with a radio transmitter and receiversystern 30.

Thus it is apparent that the assemblyplates v i 3 and 14 may be positioned closely together or e widely separated to theliull extent of the looped cable, to comply with the tail fins-thickness By such an arrangement, it has been found that the field pattern of radiation and'characteristic impedance is notafiectedby separation ofzthe two sections of antenna and-=l22by the aircrafts tail For llhahig'h frequencies that are herein contemplated the extent-ofthe metallic surface or. the fin is, so great as to constitute a complete shield betweenthe twosections of the antenna; There isthus no coupling and no reaction between; the. two. sections other than through cable 21., Thus there: is no change in their reaction or impedance whenltheir separation is changed by placing them ,on fins of different thicknesses. 1 H p In use, the assembly plate 4,3,with antenna sec,- tion li-bolted theret -betweenreflector l5. and director His fastened to one. face 2:7 of the aircraftstail fin. Plate Miwith antenna section 12, reflector i6, anddirector l8 similarly appended, is secured to. the opposite-face .18 of the'aircrafts tail fin 29. The fin faces, 2?. andZ-Bihaving been suitably perforated so as not 'tointeriere with the inwardly projectingxthreaded ends of an.-

, tenna, reflector and director rods, the assembly plates I3 and 14 when riveted or screwed to their respective. faces .21. and 28:are. aligned so that mating sections. of: antenna, reflector and director extend su bstantiallyin-ithe same plane in opposite directions and perpendicularly to the plane of the fin 29. When so arrayed and in circuit with a pulse transmitter and receiver through coaxial.

cable 26,-the resultant quarterwave'rad iated field or coverage is substantially that of a-c'one of-90 degrees in vertical, 60 degreesh'orizontal at half power with apex at the tail fin; the center line'of the cone angle extending parallel withthe axis of the air-craft. By suitably spacing and balanc ing the size of lthe'array theimpedance of the array-can be madefto match that of an Standard coaxial line. The pattern shape can be governed to some extent by suitablyfspa'cing the elements. The characteristic pattern oi the radiated andreflected waves will remain constant regardless of the space separation (withinp iactical limits) be 6 equipment the same antenna may be used to both transmit the pulsed wave and receive the reflected wave.

While the invention has been described in its preferred embodiment, it is contemplated that changes in the details thereof may be made withinthe spirit and scope of the invention as claimed. a e What is claimedis:

Thecombination in a two-section folded dipole directional radio antenna provided with wave refiector and director elements for transmission and reception of pulsed radio Waves, of adjustable means for' adapting said antenna for use on variable width mountings, said means comprising a pair of demountable assembly plates having mounted thereon mating sections of said antenna, reflector and director elements, and a length of coaxial multiple conductor ca'ble looped and electrically connecting said plates and antenna sections so as. to allow variable interspaced juxtaposed mounting of said plates while maintaining constant phase characteristics of said antenna.

GEORGE WILLIAM SCHIVLEY.

PAUL. SPRINGER.

REFERENCES CITED The following reierences are of record. in the filecf this patent:

UNITED- STATES PATENTS Number Name f Date 1,745,324. Yagi Jan. 28, 1930 2,110,278 Shaw Mar. 8, 1,932 1,942,594 Edwards et a1 Jan. 9, 1934 2,216,708! Kolster 1 Oct. 1, 19.40 12,199,050 Jenkins Apr. 30,1940 2,235,015 Eggers Mar. 18, 1941 2,343,136 Trevor May 27, 194d 2,258,407- Carter e Oct. '7, 1.941 2,292,791- M-ims Aug. 11, 1942 FOREIGN PATENTS Number Country Date 399,543 Great Britain Oct. 9, 1933 424,747 GreatBritain- Feb. 27, 1935 OTHER REFERENCES Garter, Simple Television Antennas, Radio at Ultra-High Frequencies, RCA Institutes Technicallfiress, Apri11940, pp 10-12. (Copy in Div. 51.) 

